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J Biol Chem. 2009 Jun 26;284(26):17883-96. doi: 10.1074/jbc.M109.001842. Epub 2009 Apr 30.

Crystal structure of a fibroblast growth factor homologous factor (FHF) defines a conserved surface on FHFs for binding and modulation of voltage-gated sodium channels.

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1
Department of Pharmacology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA.

Abstract

Voltage-gated sodium channels (Nav) produce sodium currents that underlie the initiation and propagation of action potentials in nerve and muscle cells. Fibroblast growth factor homologous factors (FHFs) bind to the intracellular C-terminal region of the Nav alpha subunit to modulate fast inactivation of the channel. In this study we solved the crystal structure of a 149-residue-long fragment of human FHF2A which unveils the structural features of the homology core domain of all 10 human FHF isoforms. Through analysis of crystal packing contacts and site-directed mutagenesis experiments we identified a conserved surface on the FHF core domain that mediates channel binding in vitro and in vivo. Mutations at this channel binding surface impaired the ability of FHFs to co-localize with Navs at the axon initial segment of hippocampal neurons. The mutations also disabled FHF modulation of voltage-dependent fast inactivation of sodium channels in neuronal cells. Based on our data, we propose that FHFs constitute auxiliary subunits for Navs.

PMID:
19406745
PMCID:
PMC2719427
DOI:
10.1074/jbc.M109.001842
[Indexed for MEDLINE]
Free PMC Article
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